sizing dies full length or neck sizer

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sundance1972

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any real advantages on using neck sizing dies regarding accuracy, case life, etc? am also interested in the x- dies, the "trim once, and you're good to go" dies from rcbs. they claim the cases will stop "growing",but am wondering is there could be a possibe problem with brass build up towards the neck, while the rest of the case thins out after a few reloads(if the cases stop "growing", where does the extra brass go? seems to me, it would build up at the neck if the shell is compressed back to original size/length, or does it maintain equal wall thickness?)
hope someone can explain this to me in english (not a lot of tech talk)
thank in advance for any help/replies!!
oh, dies would be for a 300 wby mag
 
If your loading for a magazine fed hunting rifle then you should use a FL Sizer to avoid feed problems.
If your single loading and shooting off a bench for accuracy then I would go for a Neck Sizer if the brass has already been fired in your rifle.
I have the X Dies for my .223 as well as a normal FL Sizer and a Neck Sizer. I don't really know enough about the X Die to comment on the questions you had about those.
 
sundance1972 said:
any real advantages on using neck sizing dies regarding accuracy, case life, etc? am also interested in the x- dies, the "trim once, and you're good to go" dies from rcbs. they claim the cases will stop "growing",but am wondering is there could be a possibe problem with brass build up towards the neck, while the rest of the case thins out after a few reloads(if the cases stop "growing", where does the extra brass go? seems to me, it would build up at the neck if the shell is compressed back to original size/length, or does it maintain equal wall thickness?)
hope someone can explain this to me in english (not a lot of tech talk)
thank in advance for any help/replies!!
oh, dies would be for a 300 wby mag
Click to expand...

Information from various sites (Lapua, Hornady) indicates that case life would be extended if the case is neck-sized only.

  • Lapua says neck sizing "reduces the strain on the case compared to full resizing."
  • Hornady stated that neck-sizing only "can eliminate problems of excessive head space, and align the bullet perfectly with the bore, resulting in better accuracy and longer case life." However, they also stated neck-sizing "should only be used for bolt-action rifle cases. Auto-loading, lever and pump action rifles usually require full-length resizing."

The RCBS X-Dies incorporates a mandrel and an expanding ball inside the die to prevent the lengthening of the neck. The mandrel stops the neck stretch and the expanding ball shapes the mouth of the neck so the wall of the neck is not thickened.

In RCBS's own words:
The patented X-Sizer Die eliminates the need for repeated trimming after an initial trim of .020” off the maximum case length to standardize the case. The X-Die doesn’t shorten the length of the case: the mandrel reduces the growth rate as the case grows as a result of the case mouth-contacting the mandrel during sizing. Because of an extremely close tolerance between the mandrel and die neck wall, the neck wall of the case does not thicken as the case length is pushed back. Cases repeatedly sized in the X-Die will initially grow a few thousandths of an inch, then stabilize below the maximum case length with no discernable loss of accuracy or case life.​

Great idea, IMHO, if RCBS applied that theory on a neck size only die.

I have done both full and neck resizing and can confirm that neck-sizing only reduces case stress and the cases last much longer (with moderate loads).

Full length dies stress the brass as the case gets compressed. Then firing expands the case again and hence another stress. Brass like most metal will experience fatigue and will eventually crack.

Cracked38Sup-1.jpg


Neck sizing only allows the brass to remain in an expanded state conforming to the shape of the chamber. Repeat firing will try to expand the case again but all metal rebound somewhat with its elasticity, hence, the the expansion becomes unnotably small (with moderate loads).

Both neck-sizing and full length sizing will stretch the neck in time but rate varies. Case trimming is required for both if cases have been re-used a few times.

As for as accuracy goes, both methods has shown similar performance for me. However, if you consider neck-size only, make a note of the observation below:

I reload 338-378 Wby Mag. On this, I only resize the neck. Taking measurements of the cases, the middle section of a new case measures (with a caliper) precisely at 9/16". After firing with a moderate load (not hot) of 125 gr of H50BMG powder, the case expanded 1/128" but still goes into the chamber without problems. The used cases has not shown any notable expansion on subsequent re-use of the case after the initial expansion.

My friend hot loads his 308 Winchester. When he tried neck-size only, a case got stuck in the chamber after firing and need to punch the case out with a cleaning rod.
​

Note that I emphasized "moderate load" many times -- Less stress on your brass and your gun.

Happy reloading!
 
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CyaN1de said it right for hunting full lenght resize, but for target and bench shooting and some types of hunting I only necksize and you can use the Lee collett dies easy to use and no lub required, but the are not the best because they work the brass one more time than Redding Competition bushing dies Titanium also no lube required, I have seen fellows load there brass over 25 times, the least time you work the neck size the longer the brass lasts. and for seating the bullets the Redding and other benchrest seaters are much better they never touch the tip of bullet like some other dies do.
some good info to read here
http://www.6mmbr.com/articles.html
 
: [INDENT said:
The patented X-Sizer Die eliminates the need for repeated trimming after an initial trim of .020” off the maximum case length to standardize the case. The X-Die doesn’t shorten the length of the case: the mandrel reduces the growth rate as the case grows as a result of the case mouth-contacting the mandrel during sizing. Because of an extremely close tolerance between the mandrel and die neck wall, the neck wall of the case does not thicken as the case length is pushed back. Cases repeatedly sized in the X-Die will initially grow a few thousandths of an inch, then stabilize below the maximum case length with no discernable loss of accuracy or case life.[/INDENT]

:confused:
i apologize if i sound a little retarded here, but some of this still doesn't make sense to me. according to my reloading books, the max case length for my 300 wby is 2.825 with a trim length of 2.815 , is it safe to trim off the extra 10 thou? i seat the bullets to a max oal of 3.56 to fit the magazine.

rcbs' statement doesn't sound quite right, either. "the x-die doesn't shorten the length of the case", then "the neck wall of the case does not thicken as the case length is pushed back". correct me if i'm wrong, but if "the case length is pushed back", would that not make it shorter??? and where does the brass that is being "pushed back" wind up, just below the neck???
i've been a welder/fabricator for about 16yrs (maybe that's why i'm a little retarded!!lol) so i know a fair bit on metal expansion, it has to go somewhere!!!
ps please feel free to add your favorite "dumb welder" jokes, there might be a few i haven't heard yet!!!
Click to expand...
 
sundance1972 said:
The patented X-Sizer Die eliminates the need for repeated trimming after an initial trim of .020” off the maximum case length to standardize the case. The X-Die doesn’t shorten the length of the case: the mandrel reduces the growth rate as the case grows as a result of the case mouth-contacting the mandrel during sizing. Because of an extremely close tolerance between the mandrel and die neck wall, the neck wall of the case does not thicken as the case length is pushed back. Cases repeatedly sized in the X-Die will initially grow a few thousandths of an inch, then stabilize below the maximum case length with no discernable loss of accuracy or case life.​

:confused:
i apologize if i sound a little retarded here, but some of this still doesn't make sense to me. according to my reloading books, the max case length for my 300 wby is 2.825 with a trim length of 2.815 , is it safe to trim off the extra 10 thou? i seat the bullets to a max oal of 3.56 to fit the magazine.

rcbs' statement doesn't sound quite right, either. "the x-die doesn't shorten the length of the case", then "the neck wall of the case does not thicken as the case length is pushed back". correct me if i'm wrong, but if "the case length is pushed back", would that not make it shorter??? and where does the brass that is being "pushed back" wind up, just below the neck???
i've been a welder/fabricator for about 16yrs (maybe that's why i'm a little retarded!!lol) so i know a fair bit on metal expansion, it has to go somewhere!!!
ps please feel free to add your favorite "dumb welder" jokes, there might be a few i haven't heard yet!!!
Click to expand...


Perhaps some diagram will help. Here is the decapping pin with the mandrel. The cut away view:
RCBSMandrelofXDie.jpg
XDieexploded.jpg

Note: The mandrel's depth is adjustable with the decapping pin.


Have a good look here:

XDieexploded-1.jpg


According to RCBS's claim, the case can be trimmed to 0.02" below max. As the cases are put throught subsequent resizing, it will gradually grow in length. However, since the gap between the inside wall of the die is fairly tight, the grown in length will stop and the thickening of the neck wall is governed. Read the instructions provided with the link below. In the instructions it mentioned of the expansion you were concerned about and tells you how you can adjust the mandrel to correct the issue.

http://www.rcbs.com/downloads/instructions/XDieProductInstructions.pdf
 
I use neck size dies if reloading cases fired from the same rifle. One very big advantage to neck size dies is that you don't have to lube the cases therefore no cleanup involved.
 
sundance1972 said:
any real advantages on using neck sizing dies regarding accuracy, case life, etc? am also interested in the x- dies, the "trim once, and you're good to go" dies from rcbs. they claim the cases will stop "growing",but am wondering is there could be a possibe problem with brass build up towards the neck, while the rest of the case thins out after a few reloads(if the cases stop "growing", where does the extra brass go? seems to me, it would build up at the neck if the shell is compressed back to original size/length, or does it maintain equal wall thickness?)
hope someone can explain this to me in english (not a lot of tech talk)
thank in advance for any help/replies!!
oh, dies would be for a 300 wby mag
Click to expand...

Sundance, I very rarely FLS with my work rifles mainly because I have tight neck chambers, run moderate pressures and find that the accuracy is slightly better when neck sized....besides which I am lazy enough to not like mucking about with FLS if I do not have to.
The brass for my hunting rifle (7x57) is always FLS as there is absolutely no difference in accuracy, also, as I run higher than moderate pressures in this rifle I find that I do need to FLS to keep everything operating smoothly.

As to the X dies, I do not really care what they write about the necks not getting longer as the necks do not concern me (they can be trimmed), what concerns me is the brass migrating from the case head, in front of which is where case separation occurs, and to be frank I do not care if the dies are plated in gold...this will still occur with repeated use.

So to recap;
Neck size if it makes a difference to accuracy and FLS if it makes the rifle more reliable...and X dies are a pointless sales spiel.
 
We were discussing how often cases could be used at Summerland the other day. Apparently the improved cartridges have long life because of the sharp shoulders too and they don't stretch as much. I have noticed with conventional cases, e.g. 708, 308 etc, that multiple use while just neck sizing could sometimes lead to tight chambering as the number of reloadings increased, especially with heavy loads. Full length sizing will restore easy chambering under these conditions. Obviously this can be dealt with by buying new cases too. Another thing I have read, I think it was in Tubb's book on Highpower Rifle, but I don't want to misquote anybody, that sometimes full length resizing will allow better cartridge alignment with the bore. (When I find the section in the book I might repost about this.:confused:) Whenever I have compared full length resizing and neck sizing myself I haven't seen a great deal of difference in accuracy, but there is no doubt it is easier on cases as people have pointed out.
 
J Stuart said:
Sundance, I very rarely FLS with my work rifles mainly because I have tight neck chambers, run moderate pressures and find that the accuracy is slightly better when neck sized....besides which I am lazy enough to not like mucking about with FLS if I do not have to.
The brass for my hunting rifle (7x57) is always FLS as there is absolutely no difference in accuracy, also, as I run higher than moderate pressures in this rifle I find that I do need to FLS to keep everything operating smoothly.

As to the X dies, I do not really care what they write about the necks not getting longer as the necks do not concern me (they can be trimmed), what concerns me is the brass migrating from the case head, in front of which is where case separation occurs, and to be frank I do not care if the dies are plated in gold...this will still occur with repeated use.

So to recap;
Neck size if it makes a difference to accuracy and FLS if it makes the rifle more reliable...and X dies are a pointless sales spiel.
Click to expand...

:D my thoughts exactly with the brass migration!! i run fairly hot loads through my 300 , it won't group very good with lower powder charges for some reason, and case separation is something i think about almost every time i shoot.
thanks for all the info you guy's have posted so far!! guess i'll stick with my full length die set for now as this is my primary hunting rifle and reliability is a lot more important to me than gaining a bit of accuracy. it already shoots about 3/4''@100yrds, pretty damn good for a plain jane vanguard, in my opinion. maybe i'll get another rifle to 'play with' soon, as friends of mine are trying to talk me into going distance shooting with them (they're out popping balloons at 960 yards so far!!). then i can start trying different dies and components without having to worry about jamming the gun and having a wounded animal running around while i'm trying to fix it.
again, thanks for all the help/replies!!:wave:
 
Sundance1972,
If you are worrying about incipent case separation it is easy checked with a wire hook dragged down the interior of the case. If it grabs in the ring it's garbage, if it doesn't you're good for at least one more firing. If you are parting cases your FLS die isn't adjusted properly. Forget anything about adjusting the die to the shell-holder and set it to barely kiss the shoulder of the case.
 
The RCBS case micrometer is a great tool, as excessive headspace caused by incorrect die set-up is the most common cause of case-head seperation. Not sure if they have them for belted cartridges.

Regards,

Peter
 
Sorry Peter I should have given more detail in my question. I have used Wilson Case Gages to set full length dies for many years and they do (did?) make adjustable case gages for magnums, i.e. belted cases. The adjustable gage allows you to take a fired case and adjust the position of the gage to match the belt in relation to the case shoulder after firing. Since firing pin thrust is supported on the belt in a belted case, rather than the shoulder as in cases without a belt, the main concern is to minimize wear and tear on the case during full-length resizing by adjusting the full length die using the gage and ensuring that the minimal amount of sizing is done. I'm not familiar with the RCBS tool, but suspect it would work the same way.
 
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